For a responsive glass used in a glass electrode, depending on a storage state and a usage state, an impurity (stain) may adhere to a hydrated layer formed on the surface of the responsive glass. As known, the responsivity of such glass electrode using the responsive glass lowers due to inhibition of electrode reaction or the like.
An example of a method for recovering the lowering of the responsivity of the glass electrode is a method for cleaning the responsive glass described in Patent Literature 1.
In the method described in Patent Literature 1, the responsive glass is cleaned by immersing the responsive glass in a drug solution (for example, hydrofluoric acid) fed into a cleaning bath for a predetermined time.